README

== Money

This library makes it easier to deal with Money values, storing them as integers to avoid floating-point math errors.

== Download

Preferred method of installation is gem: 

  gem install --source http://gems.github.com collectiveidea-money 

You can find the source at:
  
  http://github.com/collectiveidea/money

== Rails

There is a rails extension that makes it easier to store money values in the database.

  class Product < ActiveRecord::Base
    money :price
    validates_numericality_of :price_in_cents, :greater_than => 0
  end

This assumes that there is a price_in_cents (integer) column in the database, which can
be changed by passing the :cents option.  You can also specify the :currency option to
save the currency to a field in the database.

  class Room < ActiveRecord::Base
    money :rate, :cents => :rate_cents, :currency => :rate_currency
    money :discount, :cents => :discount_cents
  end

You can set the attribute to a String, Fixnum, or Float and it will call #to_money to
convert it to a Money object.  This makes it convenient for using money fields in forms.

  r = Room.new :rate => "100.00"
  r.rate  # returns <Money:0x249ef9c @currency="USD", @cents=10000>

By default, money values will be stored with a precision of 2 (cents). If you need to store different precisions, such as to the nearest tenth of a cent, you can specify the +:precision+ option:

  class Room < ActiveRecord::Base
    money :rate, :precision => 3
  end

  r = Room.new :rate => "100"
  r.rate.format  # returns $100.000
  r.rate = "100.995"
  r.rate.format  # returns $100.995

To use the Rails functionality, install money as a plugin, or require 'money/rails'.
This version is compatible with Rails 2.2.  For compatibility with previous versions of
Rails, check out the rails-2.1 branch.
  
== Class configuration

Two const class variables are available to tailor Money to your needs. 
If you don't need currency exchange at all, just ignore those.

=== Default Currency

By default Money defaults to USD as its currency. This can be overwritten using

  Money.default_currency = "CAD"
  
If you use rails, the environment.rb is a very good place to put this. 

=== Currency Exchange

The second parameter is a bit more complex. It lets you provide your own implementation of the 
currency exchange service. By default Money throws an exception when trying to call .exchange_to. 

A second minimalist implementation is provided which lets you supply custom exchange rates:

  Money.bank = VariableExchangeBank.new 
  Money.bank.add_rate("USD", "CAD", 1.24515)
  Money.bank.add_rate("CAD", "USD", 0.803115)
  Money.us_dollar(100).exchange_to("CAD") => Money.ca_dollar(124)
  Money.ca_dollar(100).exchange_to("USD") => Money.us_dollar(80)

There is nothing stopping you from creating bank objects which scrape www.xe.com for the current rates or just return rand(2)
  
== Code

If you have any improvements please email them to tobi [at] leetsoft.com